This disclosure is directed to devices and methods for collecting and distributing light from a light emitting diode (LED) emitter onto a phosphor.
LEDs are commonly used in lighting markets as light sources and typically produce light which is perceived by the human eye as a single color. For example, some of the colored light emitted by an LED may include red, blue and green. However, lighting markets such as task lighting for outdoor and interior uses, automotive lights, copier lamps in xerographic machines, and lamps in scanners use white light. Therefore, an approach for using the colored light emitted from an LED to generate white light involves using a phosphor layer to absorb some or all of the light emitted from the LED. After the light passes through the phosphor layer, some of the light is absorbed, converted, and emitted in a range of lower wavelengths. Some of the light is transmitted through the phosphor. The combination of the phosphor converted light and the transmitted light is perceived as white.
Conventional devices combining LEDs with phosphor layers to collect and combine the light emitted from the LED to generate white light are known. Some conventional solutions use total internal reflection to collect the light generated from the LED, as disclosed in U.S. Patent Application Publication No. 2005/0117125, which requires optical alignment and surfaces which must remain free of contact in order to provide the required functionality. Further, U.S. Patent Application Publication No. 2006/0170335 discloses a device using a reflector cup where the sides of the reflector cup are a rough surface. Additionally, the use of short wave pass filters and long wave pass filters, in addition to the phosphor layers, are disclosed in U.S. Pat. No. 5,813,752; U.S. Pat. No. 6,994,453; and U.S. Pat. No. 7,210,977.
Additionally, conventional devices use refraction to collect and distribute the light from the LED to the phosphor layer, as disclosed in U.S. Pat. No. 7,108,386, which discloses a non-imaging optical coupler to collect the light from the LED.
Another conventional solution for collecting and distributing light emitted from an LED onto a phosphor surface includes forming a small hollow reflective cavity by rolling a high reflectance film and inserting the rolled film into a molded plastic part, as illustrated in FIG. 1. However, in this solution, since the reflectance film is inserted into the molded plastic part, it is difficult to adopt a consistent configuration within the cavity. Further, the film may become twisted and folded preventing efficient collection of light from the LED.
Drawbacks of the above-discussed conventional devices and methods for collecting and distributing light emitted from an LED onto a phosphor surface include difficulty in obtaining consistent geometry when using the rolled film and difficulty of assembly of the hollow reflective cavity. Conventional solutions also require the phosphor surface to be larger in area than the LED emitter surface.